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| Home > Publications database > Performance of Plasma Facing Materials under Thermal and Plasma Exposure |
| Book/Dissertation / PhD Thesis | FZJ-2017-03395 |
2017
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-226-9
Please use a persistent id in citations: http://hdl.handle.net/2128/14541
Abstract: A relatively clean, safe, and promising solution to cover the globally increasing energy demand but also to avoid energy supply problems could be nuclear fusion. In recent decades, this ambitious project, to make energy generation via fusion possible, demanded a lot of work and the construction of the experimental fusion reactor ITER (latin for "the way") in Cadarache, South France, plays an important role to the next big step forward. ITER, a large scale experiment, will demonstrate the scientific and technological feasibility of nuclear fusion and should test all key technologies that are necessary for the next steps, which will be a demonstration power plant (DEMO) and finally a commercial fusion power plant. Furthermore, potential plasma facing materials (PFMs) for in-vessel components have to sustain heat fluxes, neutronic volumetric heating and neutron activation, electromagnetic loads, and environment and safety requirements just to list the most significant ones. At this time beryllium and tungsten are the PFMs in ITER, for DEMO it could be ferritic martensitic steel in addition to tungsten. In this context, this work examines two materials, tungsten und stainless steel, from the material scientific point of view under ITER and DEMO relevant heat and particle fluxes. Building on the results of former works, pure tungsten was exposed in the linear plasma device PSI-2 to sequential and simultaneous transient thermal loads with absorbed power densities up to 0.76 GW/m² and pure deuterium plasma and deuterium plasma with 6 % helium content, respectively. Furthermore, base temperatures of 400 °C and 730 °C were used and the pulse number was limited to a maximum of 1000 to cover a wide range of loading conditions within the available machine time. The results of this campaign identified that the microstructure, the order of exposure as well as the loading parameters have a substantial impact on the surface modification and damage behaviour and furthermore, that deuterium and helium exacerbates the material performance considerably. In addition, high pulse number tests ($\le$ 100, 000 pulses) with deuterium plasma background and an absorbed power density of 0.38 GW/m$^{2}$ were executed to quantify fatigue effects. These experiments led not only to tremendous plastic deformations, microstructural changes like subgrain formation and recrystallisation, but also to the formation of nanostructures and helium induced bubbles below the sample surface. In matters of ITER, where more than 106 transient events are expected, these results indicate severe disturbances of the operation as well as detractions of plasma facing components (PFCs).
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